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One or more cold cathode fluorescent lamps (CCFL) or External Electrode Fluorescent lamps (EEFL) are generally used as backlight lamps for an LCD module in flat panel displays (e.g., liquid crystal displays, plasma display panels, plasma low-profile, and liquid crystal on silicon). One or more of the backlight lamps in the LCD module are typically driven by a DC-AC inverter, which takes a DC (Direct Current) signal with a voltage of, e.g., 5 to 24 volts from a DC-DC converter, and transforming such into an appropriate AC (Alternating Current) signal.
A typical power supply system for supplying power to the backlight lamps is shown in FIG. 1. The power supply system includes an AC source input 102 from a socket passing through an AC-DC rectifier circuit 106, a Power Factor Correction (PFC) boost circuit 108, then either a first DC-DC converter circuit 109 and a DC-AC inverter circuit 111 to provide the backlight lamps 112 with AC power, or a second DC-DC converter circuit 114 to provide DC power to an LCD panel 116 or other elements. The typical power supply system requires multiple conversions from AC to DC and back to AC. For instance, an input AC voltage of 90-132 Vac or 180-264 Vac is first converted to a DC voltage of 120-190 Vdc or 250 or 380 Vdc via the AC-DC rectifier 106 and PFC boost circuit 108, and then either converted to an output DC voltage of 12 Vdc or 5 Vdc, or converted to an output AC voltage appropriate for the backlight lamps via DC-DC converter 109 and DC-AC inverter. As a result, such system occupies large space, yields high power consumption, and incurs high material or production costs. Additionally, such system has lower power efficiency from a higher power loss.